U.S. patent application number 11/547389 was filed with the patent office on 2008-11-27 for control method and controller for pwm cyclo-converter.
This patent application is currently assigned to Kabushiki Kaisha Yaskawa Denki. Invention is credited to Hidenori Hara, Jun-Koo Kang, Eiji Yamamoto.
Application Number | 20080291698 11/547389 |
Document ID | / |
Family ID | 35125410 |
Filed Date | 2008-11-27 |
United States Patent
Application |
20080291698 |
Kind Code |
A1 |
Yamamoto; Eiji ; et
al. |
November 27, 2008 |
Control Method and Controller for Pwm Cyclo-Converter
Abstract
A control method for a PWM cyclo-converter is provided in which
a voltage can be accurately generated even when a voltage command
is small. In the PWM cyclo-converter, the turning on and off
operations of two-way semiconductor switch are repeated at
intervals of short time. As switching patterns, within the
intervals of short time, a first terminal of output side terminals
outputs in order a maximum potential phase P, an intermediate
potential phase M and the maximum potential phase N, a second
terminal of the output side terminals outputs in order the maximum
potential phase P, the intermediate potential phase M, a minimum
potential phase N, the intermediate potential phase M and the
maximum potential phase P, and a third terminal of the output side
terminals outputs in order the intermediate potential phase M, the
minimum potential phase N and the intermediate potential phase
M.
Inventors: |
Yamamoto; Eiji; (Fukuoka,
JP) ; Hara; Hidenori; (Fukuoka, JP) ; Kang;
Jun-Koo; (Fukuoka, JP) |
Correspondence
Address: |
SUGHRUE-265550
2100 PENNSYLVANIA AVE. NW
WASHINGTON
DC
20037-3213
US
|
Assignee: |
Kabushiki Kaisha Yaskawa
Denki
Fukuoka
JP
|
Family ID: |
35125410 |
Appl. No.: |
11/547389 |
Filed: |
March 25, 2005 |
PCT Filed: |
March 25, 2005 |
PCT NO: |
PCT/JP2005/005509 |
371 Date: |
January 18, 2007 |
Current U.S.
Class: |
363/10 |
Current CPC
Class: |
H02M 3/33507
20130101 |
Class at
Publication: |
363/10 |
International
Class: |
H02M 5/297 20060101
H02M005/297 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2004 |
JP |
2004-104598 |
Claims
1-17. (canceled)
18. A method for controlling a PWM cyclo-converter as a power
converter for directly connecting each phase of a three-phase ac
power source to each phase of the power converter having
three-phase outputs by a two-way semiconductor switch that is a
combination of two one-way semiconductor switches supplying
electric current only in one direction and capable of being
respectively independently turned on and off, wherein when the
phase of the highest potential of the three-phase ac power source
is called a maximum potential phase, the phase of an intermediate
potential is called an intermediate potential phase and the phase
of the lowest potential is called a minimum potential phase, the
method comprising: a step for selectively turning the two-way
semiconductor switch on and off; and a step for outputting the
maximum potential phase, the intermediate potential phase and the
minimum potential phase to output side terminals.
19. The method for controlling a PWM cyclo-converter according to
claim 18, wherein the maximum potential phase and the minimum
potential phase are alternately outputted through the intermediate
potential phase by a dipolar modulation in the PWM
cyclo-converter.
20. The method for controlling a PWM cyclo-converter according to
claim 18, wherein the turning on and off operations of the two-way
semiconductor switch are repeated at intervals of short time,
within the intervals of short time, a first terminal of the output
side terminals outputs in order the maximum potential phase, the
intermediate potential phase and the maximum potential phase, a
second terminal of the output side terminals outputs in order the
maximum potential phase, the intermediate potential phase, the
minimum potential phase, the intermediate potential phase and the
maximum potential phase, and a third terminal of the output side
terminals outputs in order the intermediate potential phase, the
minimum potential phase and the intermediate potential phase.
21. The method for controlling a PWM cyclo-converter according to
claim 20, wherein the potentials are switched in nine sections of
one cycle of carrier in such a way that: in a first section and a
ninth section, the maximum potential, the maximum potential and the
intermediate potential are connected to three output side
terminals, in a second section and an eighth section, the maximum
potential, the intermediate potential and the intermediate
potential are connected to the three output side terminals, in a
third section and a seventh section, the intermediate potential,
the intermediate potential and the intermediate potential are
connected to the three output side terminals, in a fourth section
and a sixth section, the intermediate potential, the intermediate
potential and the minimum potential are connected to the three
output side terminals, and in a fifth section, the intermediate
potential, the minimum potential and the minimum potential are
connected to the three output side terminals.
22. The method for controlling a PWM cyclo-converter according to
claim 20, wherein when a phase in which the absolute value of an
input voltage is maximum is positive, the potentials are switched
in such a way that: in a first section and a ninth section, the
intermediate potential, the minimum potential and the minimum
potential are connected to three output side terminals, in a second
section and an eighth section, the intermediate potential, the
intermediate potential and the minimum potential are connected to
the three output side terminals, in a third section and a seventh
section, the intermediate potential, the intermediate potential and
the intermediate potential are connected to the three output side
terminals, in a fourth section and a sixth section, the maximum
potential, the intermediate potential and the intermediate
potential are connected to the three output side terminals, and in
a fifth section, the maximum potential, the maximum potential and
the intermediate potential are connected to the three output side
terminals.
23. The method for controlling a PWM cyclo-converter according to
claim 20, wherein the potentials are switched in eleven sections of
one cycle of carrier in such a way that: in a first section and an
eleventh section, the maximum potential, the maximum potential and
the maximum potential are connected to the three output side
terminals, in a second section and a tenth section, the maximum
potential, the maximum potential and the intermediate potential are
connected to the three output side terminals, in a third section
and a ninth section, the maximum potential, the intermediate
potential and the intermediate potential are connected to the three
output side terminals, in a fourth section and an eighth section,
the intermediate potential, the intermediate potential and the
intermediate potential are connected to the three output side
terminals, in a fifth section and a seventh section, the
intermediate potential, the intermediate potential and the minimum
potential are connected to the three output side terminals and in a
sixth section, the intermediate potential, the minimum potential
and the minimum potential are connected to the three output side
terminals.
24. The method for controlling a PWM cyclo-converter according to
claim 20, wherein when a phase in which the absolute value of an
input voltage is maximum is positive, the potentials are switched
in such a way that: in a first section and an eleventh section, the
minimum potential, the minimum potential and the minimum potential
are connected to three output side terminals, in a second section
and a tenth section, the intermediate potential, the minimum
potential and the minimum potential are connected to the three
output side terminals, in a third section and a ninth section, the
intermediate potential, the intermediate potential and the minimum
potential are connected to the three output side terminals, in a
fourth section and an eighth section, the intermediate potential,
the intermediate potential and the intermediate potential are
connected to the three output side terminals, in a fifth section
and a seventh section, the maximum potential, the intermediate
potential and the intermediate potential are connected to the three
output side terminals, and in a sixth section, the maximum
potential, the maximum potential and the intermediate potential are
connected to the three output side terminals.
25. The method for controlling a PWM cyclo-converter according to
claim 20, wherein the connecting time of the first section and the
ninth section is obtained from a formula (1), the connecting time
of the second section and the eighth section is obtained from a
formula (2), the connecting time of the third section and the
seventh section is obtained from a formula (3), the connecting time
of the fourth section and the sixth section is obtained from a
formula (4), and the connecting time of the fifth section is
obtained form a formula (5) to switch the potentials, [Mathematical
Formula 1] connecting time of sections 1 and 9 = E max T s ( V mid
- V min ) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) } (
1 ) connecting time of sections 2 and 8 = E max T s ( V max - V mid
) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) } ( 2 )
connecting time of sections 3 and 7 = T s 2 ( 1 - ( E max - E min )
( V max - V min ) { E max ( E max - E mid ) - E min ( E mid - E min
) } ) ( 3 ) connecting time of sections 4 and 6 = - E min T s ( V
mid - V min ) 2 { E max ( E max - E mid ) - E min ( E mid - E min )
} ( 4 ) connecting time of section 5 = - 2 E min T s ( V max - V
mid ) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) } ( 5 )
##EQU00016## Ts: repeating time of sections 1 to 9 Vmax: maximum
value of output phase voltage command Vmid: intermediate value of
output phase voltage command Vmin: minimum value of output phase
voltage command Emax: maximum value of input voltage Emid:
intermediate value of input voltage Emin: minimum value of input
voltage.
26. The method for controlling a PWM cyclo-converter according to
claim 20, wherein when the phase in which the absolute value of the
input voltage is maximum is positive, the connecting time of the
first section and the ninth section is obtained from a formula (6),
the connecting time of the second section and the eighth section is
obtained from a formula (7), the connecting time of the third
section and the seventh section is obtained from a formula (8), the
connecting time of the fourth section and the sixth section is
obtained from a formula (9), and the connecting time of the fifth
section is obtained form a formula (10) to switch the potentials,
[Mathematical Formula 2] connecting time of sections 1 and 9 = - E
min T s ( V max - V mid ) 2 { E max ( E max - E mid ) - E min ( E
mid - E min ) } ( 6 ) connecting time of sections 2 and 8 = - E min
T s ( V mid - V min ) 2 { E max ( E max - E mid ) - E min ( E mid -
E min ) } ( 7 ) connecting time of sections 3 and 7 = T s 2 ( 1 - (
E max - E min ) ( V max - V min ) { E max ( E max - E mid ) - E min
( E mid - E min ) } ) ( 8 ) connecting time of sections 4 and 6 = E
max T s ( V max - V mid ) 2 { E max ( E max - E mid ) - E min ( E
mid - E min ) } ( 9 ) connecting time of section 5 = 2 E max T s (
V mid - V min ) 2 { E max ( E max - E mid ) - E min ( E mid - E min
) } ( 10 ) ##EQU00017## Ts: repeating time of sections 1 to 9 Vmax:
maximum value of output phase voltage command Vmid: intermediate
value of output phase voltage command Vmin: minimum value of output
phase voltage command Emax: maximum value of input voltage Emid:
intermediate value of input voltage Emin: minimum value of input
voltage.
27. The method for controlling a PWM cyclo-converter according to
claim 20, wherein the connecting time of the second section and the
tenth section is obtained from a formula (1), the connecting time
of the third section and the ninth section is obtained from a
formula (2), the connecting time of the total sections of the first
section+the fourth section and the total sections of the eighth
section+the eleventh section is obtained from a formula (3), the
connecting time of the fifth section and the seventh section is
obtained from a formula (4), and the connecting time of the sixth
section is obtained form a formula (5) to switch the potentials,
[Mathematical Formula 3] connecting time of sections 2 and 10 = E
max T s ( V mid - V min ) 2 { E max ( E max - E mid ) - E min ( E
mid - E min ) } ( 1 ) connecting time of sections 3 and 9 = E max T
s ( V max - V mid ) 2 { E max ( E max - E mid ) - E min ( E mid - E
min ) } ( 2 ) total time of sections 1 + 4 and total time of
sections 8 + 11 = T s 2 ( 1 - ( E max - E min ) ( V max - V min ) {
E max ( E max - E mid ) - E min ( E mid - E min ) } ) ( 3 )
connecting time of sections 5 and 7 = - E min T s ( V mid - V min )
2 { E max ( E max - E mid ) - E min ( E mid - E min ) } ( 4 )
connecting time of sections 6 = - 2 E min T s ( V max - V mid ) 2 {
E max ( E max - E mid ) - E min ( E mid - E min ) } ( 5 )
##EQU00018## Ts: repeating time of sections 1 to 11 Vmax: maximum
value of output phase voltage command Vmid: intermediate value of
output phase voltage command Vmin: minimum value of output phase
voltage command Emax: maximum value of input voltage Emid:
intermediate value of input voltage Emin: minimum value of input
voltage.
28. The method for controlling a PWM cyclo-converter according to
claim 20, wherein when the phase in which the absolute value of the
input voltage is maximum is positive, the connecting time of the
second section and the tenth section is obtained from a formula
(6), the connecting time of the third section and the ninth section
is obtained from a formula (7), the connecting time of the total
sections of the first section+the fourth section and the total
sections of the eighth section+the eleventh section is obtained
from a formula (8), the connecting time of the fifth section and
the seventh section is obtained from a formula (9), and the
connecting time of the sixth section is obtained form a formula
(10) to switch the potentials, [Mathematical Formula 4] connecting
time of sections 2 and 10 = - E min T s ( V max - V mid ) 2 { E max
( E max - E mid ) - E min ( E mid - E min ) } ( 6 ) connecting time
of sections 3 and 9 = - E min T s ( V mid - V min ) 2 { E max ( E
max - E mid ) - E min ( E mid - E min ) } ( 7 ) total time of
sections 1 + 4 and total time of sections 8 + 11 = T s 2 ( 1 - ( E
max - E min ) ( V max - V min ) { E max ( E max - E mid ) - E min (
E mid - E min ) } ) ( 8 ) connecting time of sections 5 and 7 = E
max T s ( V max - V mid ) 2 { E max ( E max - E mid ) - E min ( E
mid - E min ) } ( 9 ) connecting time of sections 6 = 2 E max T s (
V mid - V min ) 2 { E max ( E max - E mid ) - E min ( E mid - E min
) } ( 10 ) ##EQU00019## Ts: repeating time of sections 1 to 11
Vmax: maximum value of output phase voltage command Vmid:
intermediate value of output phase voltage command Vmin: minimum
value of output phase voltage command Emax: maximum value of input
voltage Emid: intermediate value of input voltage Emin: minimum
value of input voltage.
29. The control method for a PWM cyclo-converter according to claim
20, wherein the potentials are switched in nine sections of one
cycle of carrier, when the phase in which the absolute value of the
input voltage is maximum is negative, the potentials are switched
in accordance with the sequence of: in a first section and a ninth
section, the maximum potential, the maximum potential and the
intermediate potential are connected to three output side
terminals, in a second section and an eighth section, the maximum
potential, the intermediate potential and the intermediate
potential are connected to the three output side terminals, in a
third section and a seventh section, the intermediate potential,
the intermediate potential and the intermediate potential are
connected to the three output side terminals, in a fourth section
and a sixth section, the intermediate potential, the intermediate
potential and the minimum potential are connected to the three
output side terminals, and in a fifth section, the intermediate
potential, the minimum potential and the minimum potential are
connected to the three output side terminals, and when the phase in
which the absolute value of the input voltage is maximum is
positive, the potentials are switched in accordance with the
sequence of: in a first section and a ninth section, the
intermediate potential, the minimum potential and the minimum
potential are connected to three output side terminals, in a second
section and an eighth section, the intermediate potential, the
intermediate potential and the minimum potential are connected to
the three output side terminals, in a third section and a seventh
section, the intermediate potential, the intermediate potential and
the intermediate potential are connected to the three output side
terminals, in a fourth section and a sixth section, the maximum
potential, the intermediate potential and the intermediate
potential are connected to the three output side terminals, and in
a fifth section, the maximum potential, the maximum potential and
the intermediate potential are connected to the three output side
terminals.
30. The control method for a PWM cyclo-converter according to claim
20, wherein the potentials are switched in eleven sections of one
cycle of carrier, when the phase in which the absolute value of the
input voltage is maximum is negative, the potentials are switched
in accordance with the sequence of: in a first section and an
eleventh section, the maximum potential, the maximum potential and
the maximum potential are connected to the three output side
terminals, in a second section and a tenth section, the maximum
potential, the maximum potential and the intermediate potential are
connected to the three output side terminals, in a third section
and a ninth section, the maximum potential, the intermediate
potential and the intermediate potential are connected to the three
output side terminals, in a fourth section and an eighth section,
the intermediate potential, the intermediate potential and the
intermediate potential are connected to the three output side
terminals, in a fifth section and a seventh section, the
intermediate potential, the intermediate potential and the minimum
potential are connected to the three output side terminals, and in
a sixth section, the intermediate potential, the minimum potential
and the minimum potential are connected to the three output side
terminals, and when the phase in which the absolute value of the
input voltage is maximum is positive, the potentials are switched
in accordance with the sequence of: in a first section and an
eleventh section, the minimum potential, the minimum potential and
the minimum potential are connected to three output side terminals,
in a second section and a tenth section, the intermediate
potential, the minimum potential and the minimum potential are
connected to the three output side terminals, in a third section
and a ninth section, the intermediate potential, the intermediate
potential and the minimum potential are connected to the three
output side terminals, in a fourth section and an eighth section,
the intermediate potential, the intermediate potential and the
intermediate potential are connected to the three output side
terminals, in a fifth section and a seventh section, the maximum
potential, the intermediate potential and the intermediate
potential are connected to the three output side terminals, and in
a sixth section, the maximum potential, the maximum potential and
the intermediate potential are connected to the three output side
terminals.
31. The control method for a PWM cyclo-converter according to claim
20, wherein the potentials are switched to the first section to the
ninth section, when the phase in which the absolute value of the
input voltage is maximum is negative, the potentials are switched
to the first section to the ninth section in accordance with the
connecting time of: the first section and the ninth section
obtained from a formula (1), the second section and the eighth
section obtained from a formula (2), the third section and the
seventh section obtained from a formula (3), the fourth section and
the sixth section obtained from a formula (4), and the fifth
section obtained form a formula (5) to switch the potentials,
[Mathematical Formula 1] connecting time of sections 1 and 9 = E
max T s ( V mid - V min ) 2 { E max ( E max - E mid ) - E min ( E
mid - E min ) } ( 1 ) connecting time of sections 2 and 8 = E max T
s ( V max - V mid ) 2 { E max ( E max - E mid ) - E min ( E mid - E
min ) } ( 2 ) connecting time of sections 3 and 7 = T s 2 ( 1 - ( E
max - E min ) ( V max - V min ) { E max ( E max - E mid ) - E min (
E mid - E min ) } ) ( 3 ) connecting time of sections 4 and 6 = - E
min T s ( V mid - V min ) 2 { E max ( E max - E mid ) - E min ( E
mid - E min ) } ( 4 ) connecting time of section 5 = - 2 E min T s
( V max - V mid ) 2 { E max ( E max - E mid ) - E min ( E mid - E
min ) } ( 5 ) ##EQU00020## Ts: repeating time of sections 1 to 9
Vmax: maximum value of output phase voltage command Vmid:
intermediate value of output phase voltage command Vmin: minimum
value of output phase voltage command Emax: maximum value of input
voltage Emid: intermediate value of input voltage Emin: minimum
value of input voltage, and when the phase in which the absolute
value of the input voltage is maximum is positive, the potentials
are switched to the first section to the ninth section in
accordance with the connecting time of: the first section and the
ninth section obtained from a formula (6), the second section and
the eighth section obtained from a formula (7), the third section
and the seventh section obtained from a formula (8), the fourth
section and the sixth section obtained from a formula (9), and the
fifth section obtained form a formula (10) to switch the
potentials, [Mathematical Formula 2] connecting time of sections 1
and 9 = - E min T s ( V max - V mid ) 2 { E max ( E max - E mid ) -
E min ( E mid - E min ) } ( 6 ) connecting time of sections 2 and 8
= - E min T s ( V mid - V min ) 2 { E max ( E max - E mid ) - E min
( E mid - E min ) } ( 7 ) connecting time of sections 3 and 7 = T s
2 ( 1 - ( E max - E min ) ( V max - V min ) { E max ( E max - E mid
) - E min ( E mid - E min ) } ) ( 8 ) connecting time of sections 4
and 6 = E max T s ( V max - V mid ) 2 { E max ( E max - E mid ) - E
min ( E mid - E min ) } ( 9 ) connecting time of section 5 = 2 E
max T s ( V mid - V min ) 2 { E max ( E max - E mid ) - E min ( E
mid - E min ) } ( 10 ) ##EQU00021## Ts: repeating time of sections
1 to 9 Vmax: maximum value of output phase voltage command Vmid:
intermediate value of output phase voltage command Vmin: minimum
value of output phase voltage command Emax: maximum value of input
voltage Emid: intermediate value of input voltage Emin: minimum
value of input voltage.
32. The control method for a PWM cyclo-converter according to claim
20, wherein the potentials are switched to the first section to the
eleventh section, when the phase in which the absolute value of the
input voltage is maximum is negative, the potentials are switched
to the first section to the eleventh section in accordance with the
connecting time of: the second section and the tenth section
obtained from a formula (1), the third section and the ninth
section obtained from a formula (2), the total sections of the
first section+the fourth section and the total sections of the
eighth section+the eleventh section obtained from a formula (3),
the fifth section and the seventh section obtained from a formula
(4), and the sixth section obtained form a formula (5) to switch
the potentials, [Mathematical Formula 3] connecting time of
sections 2 and 10 = E max T s ( V mid - V min ) 2 { E max ( E max -
E mid ) - E min ( E mid - E min ) } ( 1 ) connecting time of
sections 3 and 9 = E max T s ( V max - V mid ) 2 { E max ( E max -
E mid ) - E min ( E mid - E min ) } ( 2 ) total time of sections 1
+ 4 and total time of sections 8 + 11 = T s 2 ( 1 - ( E max - E min
) ( V max - V min ) { E max ( E max - E mid ) - E min ( E mid - E
min ) } ) ( 3 ) connecting time of sections 5 and 7 = - E min T s (
V mid - V min ) 2 { E max ( E max - E mid ) - E min ( E mid - E min
) } ( 4 ) connecting time of sections 6 = - 2 E min T s ( V max - V
mid ) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) } ( 5 )
##EQU00022## Ts: repeating time of sections 1 to 11 Vmax: maximum
value of output phase voltage command Vmid: intermediate value of
output phase voltage command Vmin: minimum value of output phase
voltage command Emax: maximum value of input voltage Emid:
intermediate value of input voltage Emin: minimum value of input
voltage, and when the phase in which the absolute value of the
input voltage is maximum is positive, the potentials are switched
to the first section to the eleventh section in accordance with the
connecting time of: the second section and the tenth section
obtained from a formula (6), the third section and the ninth
section obtained from a formula (7), the total sections of the
first section+the fourth section and the total sections of the
eighth section+the eleventh section obtained from a formula (8),
the fifth section and the seventh section obtained from a formula
(9), and the sixth section is obtained form a formula (10) to
switch the potentials, [Mathematical Formula 4] connecting time of
sections 2 and 10 = - E min T s ( V max - V mid ) 2 { E max ( E max
- E mid ) - E min ( E mid - E min ) } ( 6 ) connecting time of
sections 3 and 9 = - E min T s ( V mid - V min ) 2 { E max ( E max
- E mid ) - E min ( E mid - E min ) } ( 7 ) total time of sections
1 + 4 and total time of sections 8 + 11 = T s 2 ( 1 - ( E max - E
min ) ( V max - V min ) { E max ( E max - E mid ) - E min ( E mid -
E min ) } ) ( 8 ) connecting time of sections 5 and 7 = E max T s (
V max - V mid ) 2 { E max ( E max - E mid ) - E min ( E mid - E min
) } ( 9 ) connecting time of sections 6 = 2 E max T s ( V mid - V
min ) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) } ( 10
) ##EQU00023## Ts: repeating time of sections 1 to 11 Vmax: maximum
value of output phase voltage command Vmid: intermediate value of
output phase voltage command Vmin: minimum value of output phase
voltage command Emax: maximum value of input voltage Emid:
intermediate value of input voltage Emin: minimum value of input
voltage.
33. An apparatus for controlling a PWM cyclo-converter for directly
connecting each phase of a three-phase ac power source to each
phase of a power converter having three-phase outputs by a two-way
semiconductor switch that is a combination of two one-way
semiconductor switches supplying electric current only in one
direction and capable of being respectively independently turned on
and off, the apparatus comprising: an input filter inserted between
the three-phase ac power source and a group of two-way switches; an
input power amplitude/phase detector for detecting a voltage from
the input side of the input filter to detect input phase voltages
Er, Es and Et and an input voltage phase .theta.e for controlling
the PWM cyclo-converter; a voltage command generator for inputting
a speed command Nref to calculate an output voltage Vref and an
output voltage phase .theta.v; and a pulse generation distributor
for calculating respectively the turning on/off times of the
two-way switches from the input phase voltages Er, Es and Et, the
input voltage phase .theta.e, the output voltage Vref and the
output voltage phase .theta.v.
34. The apparatus for controlling a PWM cyclo-converter according
to claim 33, wherein the pulse generation distributor controls the
two-way switches to be turned on/off by using a method for
controlling a PWM cyclo-converter as a power converter for directly
connecting each phase of a three-phase ac power source to each
phase of the power converter having three-phase outputs by a
two-way semiconductor switch that is a combination of two one-way
semiconductor switches supplying electric current only in one
direction and capable of being respectively independently turned on
and off, wherein when the phase of the highest potential of the
three-phase ac power source is called a maximum potential phase,
the phase of an intermediate potential is called an intermediate
potential phase and the phase of the lowest potential is called a
minimum potential phase, the method comprising: a step for
selectively turning the two-way semiconductor switch on and off;
and a step for outputting the maximum potential phase, the
intermediate potential phase and the minimum potential phase to
output side terminals.
Description
TECHNICAL FIELD
[0001] The present invention relates to a power converter that can
convert an output from an ac power source to an arbitrary frequency
and more particularly to a PWM cyclo-converter using a pulse width
modulation (PWM) control system.
RELATED ART
[0002] Since in the PWM cyclo-converter, an ac power source is
directly connected to a load side by a semiconductor element for a
power, the voltage of an output and the current of an input can be
controlled at the same time. However, since a dc capacitor is not
present in the PWM cyclo-converter as in a PWM inverter, the
voltage not lower than an input voltage cannot be outputted.
Accordingly, a two-phase modulation high in its voltage use rate is
ordinarily used (for instance, see Patent Document 1).
[0003] FIG. 10 is a diagram showing a wave form of input phase
information of a "controller for three phase/three phase PWM
cyclo-converter". The diagram shows wave forms of input current
commands ir, is and it of three phases r, s and t phases. A section
number IC designates the number of each section obtained by
dividing one cycle of the input current command at intervals of
60.degree.. The IC numbers include 0 to 5 and are respectively
represented by binary numbers of three bits. Further, a reference
signal Be is a signal of one digital bit for identifying the code
of the input current command whose absolute value is maximum. The
code of the input current command whose absolute value is maximum
when Be=0 is positive and the code of the input current command
when Be=1 is negative. Whether the absolute value of the input
current command of each input phase is minimum, intermediate or
maximum is understood depending on the Be and IC. The input phase
in which the absolute value of the input current command is maximum
is defined as an input Bas phase, the input phase in which the
absolute value of the input current command is minimum is defined
as an input Sec phase and the input phase in which the absolute
value is intermediate is defined as an input Top phase. An input
current distribution factor a designates the ratio of the
intermediate value to the minimum value of the three phase input
current commands.
[0004] On the other hand, FIG. 11 is a diagram showing a wave form
of output phase information of the controller for three phase/three
phase PWM cyclo-converter. The diagram shows wave forms of output
voltage commands Vu, Vv, Vw of three phases of u, v and w phases. A
section number OC designates the number of each section obtained by
dividing one cycle of the output voltage command at intervals of
60.degree.. The OC includes 0 to 5 and each OC is represented by a
binary number of three bits. An output phase in which an output
phase voltage command is maximum when the reference signal Be is 1
is defined as an output High phase, an output phase in which an
output phase voltage command is minimum when the reference signal
Be is 1 is defined as an output Low phase and an output phase in
which the an output phase voltage command is intermediate thereof
is defined as an output Middle phase.
[0005] An output voltage command function Fh represents a
difference between a maximum value and a minimum value of a
three-phase symmetrical sine wave having the same frequency and the
same phase of an amplitude 1 as those of the output phase voltage
command shown below the output phase voltage command in FIG. 11.
Another output voltage command function Fm represents a difference
between an intermediate value and the minimum value. On the basis
of the output voltage command functions Fh and Fm, the input
current distribution factor a of the input current command, the
reference signal Be, the phase .gamma. of the input current command
of the phase r, and power supply line voltage Vrs, Vst or the like,
a virtual dc voltage Ed, the absolute value Vh* of a line voltage
command between the output High phase and the output Low phase and
the absolute value of a line voltage command between the output
Middle phase and the output Low phase are obtained to calculate
switching timings T0h, T1h, T0m and T1m in accordance with
below-described formulas.
Ed=.DELTA.etop+a*.DELTA.esec,
In this case, .DELTA.etop: the absolute value of a line voltage
between the input Top phase and the input Bas phase, .DELTA.esec:
the absolute value between a line voltage between the input Sec
phase and the input Bas phase.
Vh*=Fh*V*
Vm*:=Fm'*V*,
T0h/T2=1-(1+a)*Vh*/Ed,
T1h/T2=1-Vh*/Ed,
T0m/T2=1-(1+a)Vm*/Ed,
T1m/T2=1-Vm*/Ed,
In this case, T2: a half cycle of a carrier frequency.
[0006] Switching patterns SP0h, SP1h, SP0m and SP1m are prepared by
the switching timings obtained in accordance with the
above-described formulas.
[0007] FIG. 12 shows diagrams illustrating the switching patterns
of the converter for three-phase/three-phase PWM cyclo-converter.
FIG. 12(a) shows the patterns SP0h and SP1h of the output High
phase and FIG. 12(b) shows the patterns SP0m and SP1m of the output
Middle phase. In the drawing, T2 designates a half cycle of a
chopping wave carrier. T0h and T1h designate comparison timings
with the carrier chopping waves of SP0h and SP1h. T0m and T1m
designate comparison timings with the carrier chopping waves of
SP0m and SP1m. PJh and PJm designate converting patterns obtained
by converting the SP0h and SP0m.
[0008] In the above-described switching patterns, for instance when
"SP1h=1 and SP0h=1", a switch between the output High phase and the
input Bas phase (the input phase in which the absolute value of the
input current command is maximum) is turned on. Further, when
"SP1h=1 and SP0h=0", a switch between the output High phase and the
input Sec phase (the input phase in which the absolute value is
minimum) is turned on. Further, when "SP1h=0 and SP0h=0", a driving
operation is carried out by a switch pattern that a switch between
the output High phase and the input Top phase (the input phase in
which the absolute value is intermediate) is turned on. Patent
Document 1: JP-A-11-341807 (FIG. 2, FIG. 3 and FIG. 5)
DISCLOSURE OF THE INVENTION
Problems to be solved by the Invention
[0009] However, in the PWM cyclo-converter disclosed in the Patent
Document 1, when an output voltage is formed only by a two-phase
modulation having one phase fixed, a phenomenon arises that voltage
accuracy is deteriorated during outputting a low voltage. This
phenomenon arises due to a commutation operation carried out not to
generate a short-circuit of an input or a release of an output when
a switching operation is performed. Thus, the pulsation or the
damping of a torque of a load to be driven may be possibly
caused.
[0010] As means for solving this problem, a three-phase modulation
is exemplified in which all three phases are switched during
outputting the low voltage. However, in the three-phase modulation,
since the three-phases of output phases are switched, a switching
loss is increased, so that a problem arises that the rating of
semiconductor elements needs to be increased or a cooling system
needs to be reexamined.
[0011] Thus, it is an object of the present invention to provide a
control method and a controller for a PWM cyclo-converter in which
a degree of freedom in control of an input current of the PWM
cyclo-converter is left and a three-phase modulation can be
realized that is high in its voltage accuracy in all speed areas
with the same switching loss as that of a two-phase modulation.
Means for Solving the Problems
[0012] In order to solve the above-described problems, according to
claim 1, there is provided a method for controlling a PWM
cyclo-converter as a power converter for directly connecting each
phase of a three-phase ac power source to each phase of the power
converter having three-phase outputs by a two-way semiconductor
switch that is a combination of two one-way semiconductor switches
supplying electric current only in one direction and capable of
being respectively independently turned on and off, wherein
[0013] when the phase of the highest potential of the three-phase
ac power source is called a maximum potential phase, the phase of
an intermediate potential is called an intermediate potential phase
and the phase of the lowest potential is called a minimum potential
phase,
[0014] the method including:
[0015] a step for selectively turning the two-way semiconductor
switch on and off; and
[0016] a step for outputting the maximum potential phase, the
intermediate potential phase and the minimum potential phase to
output side terminals.
[0017] According to claim 2, there is provided the method for
controlling the PWM cyclo-converter as in claim 1, wherein
[0018] the maximum potential phase and the minimum potential phase
are alternately outputted through the intermediate potential phase
by a dipolar modulation in the PWM cyclo-converter.
[0019] According to claim 3, there is provided the method for
controlling the PWM cyclo-converter as in claim 1, wherein
[0020] the turning on and off operations of the two-way
semiconductor switch are repeated at intervals of short time,
within the intervals of short time,
[0021] a first terminal of the output side terminals outputs in
order the maximum potential phase, the intermediate potential phase
and the maximum potential phase,
[0022] a second terminal of the output side terminals outputs in
order the maximum potential phase, the intermediate potential
phase, the minimum potential phase, the intermediate potential
phase and the maximum potential phase, and
[0023] a third terminal of the output side terminals outputs in
order the intermediate potential phase, the minimum potential phase
and the intermediate potential phase.
[0024] According to claim 4, there is provided the method for
controlling the PWM cyclo-converter as in claim 3, wherein
[0025] the potentials are switched in nine sections of one cycle of
carrier in such a way that:
[0026] in a first section and a ninth section, the maximum
potential, the maximum potential and the intermediate potential are
connected to three output side terminals,
[0027] in a second section and an eighth section, the maximum
potential, the intermediate potential and the intermediate
potential are connected to the three output side terminals,
[0028] in a third section and a seventh section, the intermediate
potential, the intermediate potential and the intermediate
potential are connected to the three output side terminals,
[0029] in a fourth section and a sixth section, the intermediate
potential, the intermediate potential and the minimum potential are
connected to the three output side terminals, and
[0030] in a fifth section, the intermediate potential, the minimum
potential and the minimum potential are connected to the three
output side terminals.
[0031] According to claim 5, there is provided the method for
controlling the PWM cyclo-converter as in claim 3, wherein
[0032] when a phase in which the absolute value of an input voltage
is maximum is negative, the potentials are switched in such a way
sequence as described in claim 4, and
[0033] when a phase in which the absolute value of an input voltage
is maximum is positive, the potentials are switched in such a way
that:
[0034] in a first section and a ninth section, the intermediate
potential, the minimum potential and the minimum potential are
connected to three output side terminals,
[0035] in a second section and an eighth section, the intermediate
potential, the intermediate potential and the minimum potential are
connected to the three output side terminals,
[0036] in a third section and a seventh section, the intermediate
potential, the intermediate potential and the intermediate
potential are connected to the three output side terminals,
[0037] in a fourth section and a sixth section, the maximum
potential, the intermediate potential and the intermediate
potential are connected to the three output side terminals, and
[0038] in a fifth section, the maximum potential, the maximum
potential and the intermediate potential are connected to the three
output side terminals.
[0039] According to claim 6, there is provided the method for
controlling the PWM cyclo-converter as in claim 3, wherein
[0040] the potentials are switched in eleven sections of one cycle
of carrier in such a way that:
[0041] in a first section and an eleventh section, the maximum
potential, the maximum potential and the maximum potential are
connected to the three output side terminals,
[0042] in a second section and a tenth section, the maximum
potential, the maximum potential and the intermediate potential are
connected to the three output side terminals,
[0043] in a third section and a ninth section, the maximum
potential, the intermediate potential and the intermediate
potential are connected to the three output side terminals,
[0044] in a fourth section and an eighth section, the intermediate
potential, the intermediate potential and the intermediate
potential are connected to the three output side terminals,
[0045] in a fifth section and a seventh section, the intermediate
potential, the intermediate potential and the minimum potential are
connected to the three output side terminals, and
[0046] in a sixth section, the intermediate potential, the minimum
potential and the minimum potential are connected to the three
output side terminals.
[0047] According to claim 7, there is provided the method for
controlling the PWM cyclo-converter as in claim 3, wherein
[0048] when a phase in which the absolute value of an input voltage
is maximum is negative, the potentials are switched in such a
sequence as described in claim 6, and
[0049] when a phase in which the absolute value of an input voltage
is maximum is positive, the potentials are switched in such a way
that:
[0050] in a first section and an eleventh section, the minimum
potential, the minimum potential and the minimum potential are
connected to three output side terminals,
[0051] in a second section and a tenth section, the intermediate
potential, the minimum potential and the minimum potential are
connected to the three output side terminals,
[0052] in a third section and a ninth section, the intermediate
potential, the intermediate potential and the minimum potential are
connected to the three output side terminals,
[0053] in a fourth section and an eighth section, the intermediate
potential, the intermediate potential and the intermediate
potential are connected to the three output side terminals,
[0054] in a fifth section and a seventh section, the maximum
potential, the intermediate potential and the intermediate
potential are connected to the three output side terminals, and
[0055] in a sixth section, the maximum potential, the maximum
potential and the intermediate potential are connected to the three
output side terminals.
[0056] According to claim 8, there is provided the method for
controlling the PWM cyclo-converter as in claim 3 or 4, wherein
[0057] the connecting time of the first section and the ninth
section is obtained from a formula (1),
[0058] the connecting time of the second section and the eighth
section is obtained from a formula (2),
[0059] the connecting time of the third section and the seventh
section is obtained from a formula (3),
[0060] the connecting time of the fourth section and the sixth
section is obtained from a formula (4), and
[0061] the connecting time of the fifth section is obtained form a
formula (5) to switch the potentials.
[Mathematical Formula 1]
[0062] connecting time of sections 1 and 9 = E max T s ( V mid - V
min ) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) } ( 1 )
connecting time of sections 2 and 8 = E max T s ( V max - V mid ) 2
{ E max ( E max - E mid ) - E min ( E mid - E min ) } ( 2 )
connecting time of sections 3 and 7 = T s 2 ( 1 - ( E max - E min )
( V max - V min ) { E max ( E max - E mid ) - E min ( E mid - E min
) } ) ( 3 ) connecting time of sections 4 and 6 = - E min T s ( V
mid - V min ) 2 { E max ( E max - E mid ) - E min ( E mid - E min )
} ( 4 ) connecting time of section 5 = - 2 E min T s ( V max - V
mid ) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) } ( 5 )
##EQU00001##
In this case, signs in the formulas are defined as described below.
Ts: repeating time of sections 1 to 9 Vmax: maximum value of output
phase voltage command Vmid: intermediate value of output phase
voltage command Vmin: minimum value of output phase voltage command
Emax: maximum value of input voltage Emid: intermediate value of
input voltage Emin: minimum value of input voltage
[0063] According to claim 9, there is provided the method for
controlling the PWM cyclo-converter as in claim 3 or 5, wherein
[0064] when a phase in which the absolute value of an input voltage
is maximum is negative, the sections 1 to 9 are connected in the
connecting times obtained in the formulas (1) to (5) described in
claim 8, and
[0065] when the phase in which the absolute value of the input
voltage is maximum is positive,
[0066] the connecting time of the first section and the ninth
section is obtained from a formula (6),
[0067] the connecting time of the second section and the eighth
section is obtained from a formula (7),
[0068] the connecting time of the third section and the seventh
section is obtained from a formula (8),
[0069] the connecting time of the fourth section and the sixth
section is obtained from a formula (9), and
[0070] the connecting time of the fifth section is obtained form a
formula (10) to switch the potentials.
[Mathematical Formula 2]
[0071] connecting time of sections 1 and 9 = - E min T s ( V max -
V mid ) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) } ( 6
) connecting time of sections 2 and 8 = - E min T s ( V mid - V min
) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) } ( 7 )
connecting time of sections 3 and 7 = T s 2 ( 1 - ( E max - E min )
( V max - V min ) { E max ( E max - E mid ) - E min ( E mid - E min
) } ) ( 8 ) connecting time of sections 4 and 6 = E max T s ( V max
- V mid ) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) } (
9 ) connecting time of section 5 = 2 E max T s ( V mid - V min ) 2
{ E max ( E max - E mid ) - E min ( E mid - E min ) } ( 10 )
##EQU00002##
In this case, signs in the formula are defined as described below.
Ts: repeating time of sections 1 to 9 Vmax: maximum value of output
phase voltage command Vmid: intermediate value of output phase
voltage command Vmin: minimum value of output phase voltage command
Emax: maximum value of input voltage Emid: intermediate value of
input voltage Emin: minimum value of input voltage
[0072] According to claim 10, there is provided the method for
controlling the PWM cyclo-converter as in claim 3 or 6, wherein
[0073] the connecting time of the second section and the tenth
section is obtained from a formula (1),
[0074] the connecting time of the third section and the ninth
section is obtained from a formula (2),
[0075] the connecting time of the total sections of the first
section+the fourth section and the total sections of the eighth
section+the eleventh section is obtained from a formula (3),
[0076] the connecting time of the fifth section and the seventh
section is obtained from a formula (4), and
[0077] the connecting time of the sixth section is obtained form a
formula (5) to switch the potentials.
[Mathematical Formula 3]
[0078] connecting time of sections 2 and 10 = E max T s ( V mid - V
min ) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) } ( 1 )
connecting time of sections 3 and 9 = E max T s ( V max - V mid ) 2
{ E max ( E max - E mid ) - E min ( E mid - E min ) } ( 2 ) total
time of sections 1 + 4 and total time of sections 8 + 11 = T s 2 (
1 - ( E max - E min ) ( V max - V min ) { E max ( E max - E mid ) -
E min ( E mid - E min ) } ) ( 3 ) connecting time of sections 5 and
7 = - E min T s ( V mid - V min ) 2 { E max ( E max - E mid ) - E
min ( E mid - E min ) } ( 4 ) connecting time of sections 6 = - 2 E
min T s ( V max - V mid ) 2 { E max ( E max - E mid ) - E min ( E
mid - E min ) } ( 5 ) ##EQU00003##
In this case, signs in the formula are defined as described below.
Ts: repeating time of sections 1 to 11 Vmax: maximum value of
output phase voltage command Vmid: intermediate value of output
phase voltage command Vmin: minimum value of output phase voltage
command Emax: maximum value of input voltage Emid: intermediate
value of input voltage Emin: minimum value of input voltage
[0079] According to claim 11, there is provided the method for
controlling the PWM cyclo-converter as in claim 3 or 7, wherein
[0080] when the phase in which the absolute value of the input
voltage is maximum is negative, the sections 1 to 11 are connected
in the connecting times obtained by the formulas (1) to (5)
described in claim 10, and
[0081] when the phase in which the absolute value of the input
voltage is maximum is positive,
[0082] the connecting time of the second section and the tenth
section is obtained from a formula (6),
[0083] the connecting time of the third section and the ninth
section is obtained from a formula (7),
[0084] the connecting time of the total sections of the first
section+the fourth section and the total sections of the eighth
section+the eleventh section is obtained from a formula (8),
[0085] the connecting time of the fifth section and the seventh
section is obtained from a formula (9), and
[0086] the connecting time of the sixth section is obtained form a
formula (10) to switch the potentials.
[Mathematical Formula 4]
[0087] connecting time of sections 2 and 10 = - E min T s ( V max -
V mid ) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) } ( 6
) connecting time of sections 3 and 9 = - E min T s ( V mid - V min
) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) } ( 7 )
total time of sections 1 + 4 and total time of sections 8 + 11 = T
s 2 ( 1 - ( E max - E min ) ( V max - V min ) { E max ( E max - E
mid ) - E min ( E mid - E min ) } ) ( 8 ) connecting time of
sections 5 and 7 = E max T s ( V max - V mid ) 2 { E max ( E max -
E mid ) - E min ( E mid - E min ) } ( 9 ) connecting time of
sections 6 = 2 E max T s ( V mid - V min ) 2 { E max ( E max - E
mid ) - E min ( E mid - E min ) } ( 10 ) ##EQU00004##
In this case, signs in the formula are defined as described below.
Ts: repeating time of sections 1 to 11 Vmax: maximum value of
output phase voltage command Vmid: intermediate value of output
phase voltage command Vmin: minimum value of output phase voltage
command Emax: maximum value of input voltage Emid: intermediate
value of input voltage Emin: minimum value of input voltage
[0088] According to claim 12, there is provided the method for
controlling the PWM cyclo-converter as in claim 3, wherein
[0089] the potentials are switched in nine sections of one cycle of
carrier,
[0090] when the phase in which the absolute value of the input
voltage is maximum is negative, the potentials are switched in
accordance with the sequence as described in claim 4, and
[0091] when the phase in which the absolute value of the input
voltage is maximum is positive, the potentials are switched in
accordance with the sequence as described in claim 5.
[0092] According to claim 13, there is provided the method for
controlling the PWM cyclo-converter as in claim 3, wherein
[0093] the potentials are switched in eleven sections of one cycle
of carrier,
[0094] when the phase in which the absolute value of the input
voltage is maximum is negative, the potentials are switched in
accordance with the sequence as described in claim 6, and
[0095] when the phase in which the absolute value of the input
voltage is maximum is positive, the potentials are switched in
accordance with the sequence as described in claim 7.
[0096] According to claim 14, there is provided the method for
controlling the PWM cyclo-converter as in claim 3 or 5, wherein
[0097] the potentials are switched to the first section to the
ninth section,
[0098] when the phase in which the absolute value of the input
voltage is maximum is negative, the potentials are switched to the
first section to the ninth section in accordance with the
connecting times obtained in the formulas (1) to (5) described in
claim 8, and
[0099] when the phase in which the absolute value of the input
voltage is maximum is positive, the potentials are switched to the
first section to the ninth section in accordance with the
connecting times obtained in the formulas (6) to (10) described in
claim 9.
[0100] According to claim 15, there is provided the method for
controlling the PWM cyclo-converter as in claim 3 or 5, wherein
[0101] the potentials are switched to the first section to the
eleventh section,
[0102] when the phase in which the absolute value of the input
voltage is maximum is negative, the potentials are switched to the
first section to the eleventh section in accordance with the
connecting times obtained in the formulas (1) to (5) described in
claim 10, and
[0103] when the phase in which the absolute value of the input
voltage is maximum is positive, the potentials are switched to the
first section to the eleventh section in accordance with the
connecting times obtained in the formulas (6) to (10) described in
claim 11.
[0104] According to claim 16, there is provided an apparatus for
controlling a PWM cyclo-converter for directly connecting each
phase of a three-phase ac power source to each phase of a power
converter having three-phase outputs by a two-way semiconductor
switch that is a combination of two one-way semiconductor switches
supplying electric current only in one direction and capable of
being respectively independently turned on and off,
[0105] the apparatus including:
[0106] an input filter inserted between the three-phase ac power
source and a group of two-way switches;
[0107] an input power amplitude/phase detector for detecting a
voltage from the input side of the input filter to detect input
phase voltages Er, Es and Et and an input voltage phase .theta.e
for controlling the PWM cyclo-converter;
[0108] a voltage command generator for inputting a speed command
Nref to calculate an output voltage Vref and an output voltage
phase .theta.v; and
[0109] a pulse generation distributor for calculating respectively
the turning on/off times of the two-way switches from the input
phase voltages Er, Es and Et, the input voltage phase .theta.e, the
output voltage Vref and the output voltage phase .theta.v.
[0110] According to claim 17, there is provided the apparatus for
controlling the PWM cyclo-converter as in claim 16, wherein
[0111] the pulse generation distributor controls the two-way
switches to be turned on/off by using a method for controlling the
PWM cyclo-converter according to any one of claims 1 to 15.
ADVANTAGE OF THE INVENTION
[0112] According to the present invention, since a switching loss
the same as that of a two-phase modulation and a voltage accuracy
the same as that of a three-phase modulation can be simultaneously
realized and a voltage can be accurately outputted, a power
converter with low loss and good accuracy can be effectively
provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0113] FIG. 1 is a control block diagram of a PWM cyclo-converter
according to the present invention.
[0114] FIG. 2 is a diagram showing a connecting example of a
two-way switch forming a main circuit of the PWM cyclo-converter
shown in FIG. 1.
[0115] FIG. 3 is a diagram showing sections of an input phase for
explaining a switching system of the present invention.
[0116] FIG. 4 is a diagram showing sections of an output phase for
explaining the switching system of the present invention.
[0117] FIG. 5 is a diagram showing a switching pattern in an input
section of "0" and an output section of "0" in the present
invention.
[0118] FIG. 6 is a diagram showing a switching pattern in an input
section of "1" and an output section of "0" in the present
invention.
[0119] FIG. 7 shows diagrams respectively illustrating voltage wave
form examples according to the switching patterns of the present
invention.
[0120] FIG. 8 shows diagrams respectively illustrating voltage
waveform examples according to the switching patterns of the
present invention when the number of sections is 11.
[0121] FIG. 9 shows comparison diagrams of voltage wave forms
respectively for explaining effects of the present invention.
[0122] FIG. 10 is a waveform diagram of input phase information of
a usual controller for a three-phase/three-phase PWM
cyclo-converter.
[0123] FIG. 11 is a waveform diagram of output phase information of
the usual controller for a three-phase/three-phase PWM
cyclo-converter.
[0124] FIG. 12 is a diagram showing a switching pattern of the
usual controller for a three-phase/three-phase PWM
cyclo-converter.
DESCRIPTION OF REFERENCE NUMERALS AND SIGNS
[0125] 1 . . . three-phase ac power source [0126] 2 . . . input
filter [0127] 3 . . . group of two-way switches [0128] 4 . . .
input voltage amplitude/phase detector [0129] 5 . . . voltage
command generator [0130] 6 . . . pulse generation distributor
[0131] 7 . . . load motor
BEST MODE FOR CARRYING OUT THE INVENTION
[0132] Now, an embodiment of the present invention will be
described below by referring to the drawings.
First Embodiment stages indicate Vmax, Vmid and Vmin respectively
designated by Emax, Emid and Emin and lower stages respectively
designate line voltages dVmax=max-Vmin, dVmid1=Vmax-Vmid and
dVmid2=Vmid-Vmin.
[0133] In the voltage waveforms shown in FIG. 7(b), in the
sections, a reference input potential Ebase outputs the voltage
wave form when Emin=Ebase. Switching times 1 to 9 in FIG. 7(b) can
be expressed as in Table 2. The numbers of formulas in the Table
are identical with the numbers of formulas described in claims.
TABLE-US-00001 TABLE 2 Section Formula Setting time of timer 1, 9
(1) E max T s ( V mid - V min ) 2 { E max ( E max - E mid ) - E min
( E mid - E min ) } ##EQU00005## 2, 8 (2) E max T s ( V max - V mid
) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) }
##EQU00006## 3, 7 (3) T s 2 ( 1 - ( E max - E min ) ( V max - V min
) { E max ( E max - E mid ) - E min ( E mid - E min ) } )
##EQU00007## 4, 6 (4) - E min T s ( V mid - V min ) 2 { E max ( E
max - E mid ) - E min ( E mid - E min ) } ##EQU00008## 5 (5) - E
min T s ( V max - V mid ) { E max ( E max - E mid ) - E min ( E mid
- E min ) } ##EQU00009##
[0134] In the case of the input section of "0" in FIG. 3 and the
output section "0" in FIG. 4 and in the case of the input section
of "1" in FIG. 3 and the output section
[0135] FIG. 1 is a control block diagram of a PWM cyclo-converter
according to the present invention.
[0136] FIG. 2 is a diagram showing a connecting example of a
two-way switch forming a main circuit of the PWM cyclo-converter
shown in FIG. 1.
[0137] FIG. 3 is a diagram showing sections of an input phase for
explaining a switching system of the present invention.
[0138] FIG. 4 is a diagram showing sections of an output phase for
explaining the switching system of the present invention.
[0139] FIG. 5 is a diagram showing a switching pattern in an input
section of 0 and an output section of 0 in the present
invention.
[0140] FIG. 6 is a diagram showing a switching pattern in an input
section of 1 and an output section of 0 in the present
invention.
[0141] FIG. 7 shows diagrams respectively illustrating voltage wave
form examples according to the switching patterns of the present
invention.
[0142] FIG. 8 shows diagrams respectively illustrating voltage wave
form examples according to the switching patterns of the present
invention when the number of sections is 11.
[0143] FIG. 9 shows comparison diagrams of voltage wave forms
respectively for explaining effects of the present invention.
[0144] In FIG. 1, an input filter 2 is provided between a
three-phase ac power source 1 and a group of two-way switches 3
including two-way switches Sur to Swt. The outputs of the group of
two-way switches 3 are connected to a load motor 7. The input
filter 2 and the group of two-way switches 3 form a main circuit of
a PWM cyclo-converter. Voltage is detected from an input side (a
primary side) of the input filter 2 to detect input phase voltages
Er, Es and Et and an input voltage phase .theta.e necessary for
controlling the PWM cyclo-converter by an input power
amplitude/phase detector 4. On the other hand, a speed command Nref
is inputted by a voltage command generator 5 to calculate an output
voltage Vref and an output voltage phase .theta.v. A pulse
generation distributor 6 calculates the nine turning on/off times
of the two-way switches Sur to Swt from the input phase voltages
Er, Es and Et, the input voltage phase .theta.e, the output voltage
Vref and the output voltage phase .theta.v. The two-way switches
Sur to Swt may be formed by combining reverse blocking type IGBTs
inversely parallel with each other, or by combining diodes
connected in series to IGBTs inversely parallel with each other as
shown in FIG. 2.
[0145] Now, a process of the pulse generation distributor 6 will be
mainly described below in detail.
[0146] The PWM cyclo-converter is a power converter in which an
input (a power source side) is directly connected an output (a load
side) by the two-way switches and an alternating current can be
directly formed from an alternating current. As shown in FIG. 3, an
input voltage phase of the three-phase power source 1 is divided
into 12 sections. Further, as shown in FIG. 4, an output voltage
phase is divided into 6 sections. The potential of each phase of
input and output voltage continuously changes depending on the
phase.
[0147] Here, the association of FIGS. 3 to 7 respectively will be
described below.
[0148] FIG. 3 is a diagram showing sections of an input phase for
explaining a switching system of the present invention. Since an
input side is connected to a commercial power source, the input
side has a prescribed cycle as long as 50 Hz or 60 Hz. FIG. 4 is a
diagram showing sections of an output phase for explaining the
switching system of the present invention. The output phase changes
depending on the angle of an actual motor.
[0149] An output section in FIG. 4 corresponding to an input
section of "0" in FIG. 3 has 6 patterns of "0" to "5". Similarly,
an output section in FIG. 4 corresponding to an input section of
"1" in FIG. 3 also has 6 patterns of "0" to "5". An output section
in FIG. 4 corresponding to an input section of "2" in FIG. 3 also
has 6 patterns of "0" to "5". Accordingly, the output sections in
FIG. 4 corresponding to 12 sections as all the input sections "0"
to "11" in FIG. 3 include 72 patterns of 12.times.6.
[0150] FIGS. 5 and 7(a) show switch ON patterns and voltage wave
form examples respectively when the input phase is "0" and the
output phase is "0". FIGS. 6 and 7(b) show switch ON patterns and
voltage wave form examples respectively when the input phase is "1"
and the output phase is "0".
[0151] Now, when a condition is considered in which the input
section of FIG. 3 is "0" and the output section of FIG. 4 is "0",
the sections of 1 to 9 in FIG. 7(a) enter the above-described
sections many times. The above-described matter is explained by
using actual numeric values. Assuming that an input power source
has 50 Hz and an output frequency is 50 Hz, when an input is
synchronous with an output and the phases of them are the same, the
input section of "0" has 20 ms/12=1.67 ms. Assuming that a carrier
frequency has 10 kHz, since one cycle has 100 .mu.s, the patterns
shown in FIG. 7 appear 16 times or 17 times in the input section of
"0".
[0152] Now, a process of the section of "0" of the input voltage
phase and the section of "0" of the output voltage phase will be
firstly described. FIG. 5 shows the switching pattern of the
two-way switch for realizing the switching system of the present
invention. The items of a table shown in FIG. 5 will be
respectively described from the left side. An [output phase]
indicates that a relevant section is a section of "0" and an output
phase section of 0 to 60 degrees as shown in FIG. 4 and a maximum
value Vmax=Vu, an intermediate value Vmid=Vv and an minimum value
Vmin=Vw. Next [sections] a, b, c, d, and e correspond to
below-described sections shown in FIG. 7.
[0153] Next [Vmax] designates Vu herein, and represents on/off of
three terminals UR, US and UT connected to the input voltages Er,
Es and Et by three bits. [Vmax] represents "010" in the section a.
Similarly, in the section a, [Vmid] represents "001" and [Vmin]
represents "001". In the next section b, Vmax represents "010",
Vmid represents "010" and Vmin represents "001" . . . . In such a
way, the two-way switches Sur to Swt are turned on/off in
accordance with the on/off patterns shown in FIG. 5. Here, on is
designated by "1" and off is designated by
[0154] FIG. 7(a) shows voltage wave forms when a switching
operation (a comparison with a carrier or a vector calculation) is
performed in accordance with the patterns shown in FIG. 5. In FIG.
7(a), Ebase designates reference input voltage. In this section, a
voltage wave form showing Emax=Ebase is outputted. The sections 1
to 5 of the sections 1 to 9 correspond to the sections a to e of
the switching pattern diagram shown in FIG. 5. Further, P, M and N
correspond to P=a maximum value, M=an intermediate value and N=a
minimum value.
[0155] An uppermost input voltage switch block of Emax, Emid and
Emin corresponds to Vmax of the output voltage side. A next block
of Emax, Emid and Emin corresponds to Vmid. The last block of Emax,
Emid and Emin corresponds to Vmin. dVmax=Vmax-Vmin,
dVmid1=Vmax-Vmid and dVmid2=Vmid-Vmin shown below them designate
output line voltages (the above description indicates the contents
disclosed in claim 1).
[0156] Further, the sections 3 and 7 that are painted out designate
what is called zero vectors in which all switches are connected to
the intermediate phase Emid of the input voltage.
[0157] Switching times 1 to 9 shown in FIG. 7(a) can be expressed
as in Table 1. In the numbers of formulas in the Table are
identical with the numbers of formulas described in claims.
TABLE-US-00002 TABLE 1 PWM section Formula Switching time 1, 9 (6)
- E min T s ( V max - V mid ) 2 { E max ( E max - E mid ) - E min (
E mid - E min ) } ##EQU00010## 2, 8 (7) - E min T s ( V mid - V min
) 2 { E max ( E max - E mid ) - E min ( E mid - E min ) }
##EQU00011## 3, 7 (8) T s 2 ( 1 - ( E max - E min ) ( V max - V min
) { E max ( E max - E mid ) - E min ( E mid - E min ) } )
##EQU00012## 4, 6 (9) E max T s ( V max - V mid ) 2 { E max ( E max
- E mid ) - E min ( E mid - E min ) } ##EQU00013## 5 (10) 2 E max T
s ( V mid - V min ) 2 { E max ( E max - E mid ) - E min ( E mid - E
min ) } ##EQU00014##
[0158] Now, the switch ON patterns and voltage wave form examples
when the input phase in FIG. 3 is "1" and the output phase in FIG.
4 is "0" will be respectively described in accordance with FIGS. 6
and 7(b). In FIG. 6, in a section a, Vmax=Vu represents "100",
Vmid=Vv represent "100" and Vmin=Vw represents "010". In a next
section b, Vmax=Vu represents "100", Vmid=Vv represents "010" and
Vmin=Vw represents "010" . . . . (the following is the same as
described above).
[0159] In FIG. 7(b) showing the output voltage wave forms
corresponding to the switch patterns in FIG. 6, upper of "0" in
FIG. 4, the switch ON patterns and the voltage wave form examples
are respectively described above. As remaining sections, in the
case of the input section of "0" in FIG. 3 and the output sections
of "1" to "5" in FIG. 4, in the case of the input section of "1" in
FIG. 3 and the output sections of "1" to "5" in FIG. 4 and in the
case of the input sections "2" to "11" in FIG. 3 and the output
sections of "0" to "5" in FIG. 4 respectively corresponding to the
sections, the switch ON patterns and the voltage wave form examples
can be respectively obtained in the same manner.
[0160] As described above, even when the same output phases are
outputted, if the phases of the input voltage are different, FIGS.
7(a) and (b) are switched to output the output phases.
[0161] Claim 3 discloses the above-described switching patterns.
(Here, in the relation between FIGS. 7(a) and 7(b), that is, the
relation between FIG. 5 and FIG. 6, FIGS. 6 and 7(b) show a case
that when the phase in which the absolute value of the input
voltage is maximum is negative, Emin=Ebase, and FIGS. 5 and 7(a)
show a case that when the phase in which the absolute value of the
input voltage is maximum is positive, Emax=Ebase. Claim 3 discloses
the construction of FIG. 7(a)). Therefore, "the maximum potential
phase, the intermediate potential phase, the maximum potential
phase . . . . " disclosed in claim 3 means, for instance, Vmax:
from PPMMM to MMMPP. The second "maximum potential phase, the
intermediate potential phase, the minimum potential phase, the
intermediate potential phase and the maximum potential phase" means
Vmid: from PMMMN to NMMMP. The third "intermediate potential phase,
the minimum potential phase and the intermediate potential phase"
means Vmin: from MMMNN to NNMMM.
[0162] A connection to "the maximum potential, the maximum
potential and the intermediate potential" in the first and ninth
sections similarly disclosed in claim 4 means a lengthwise
arrangement of PPM in the first and ninth sections in FIG. 7(a),
that is, a column of PPM including Vmax: P, Vmid: P and Vmin: M.
The "maximum potential, the intermediate potential and the
intermediate potential" in the second and eighth sections means a
column of PMM including Vmax: P, Vmid: M and Vmin: M in the second
and eighth sections. The "intermediate potential, the intermediate
potential and the intermediate potential" in the third and seventh
sections means a column of MMM including Vmax: M, Vmid: M and Vmin:
M. The "intermediate potential, the intermediate potential and the
minimum potential" in the fourth and sixth sections means a column
of MMN including Vmax: M, Vmid: M and Vmin: N. The "intermediate
potential, the minimum potential and the minimum potential" in the
fifth section means a column of MNN including Vmax: M, Vmid: N and
Vmin: N, respectively. Claim 4 discloses a case of FIG. 7(a) that
the phase in which the absolute value of the input voltage is
maximum is negative (Emin=Ebase), and claim 5 discloses a case of
FIG. 7(b) that the phase in which the absolute value of the input
voltage is positive (Emax=Ebase) respectively.
[0163] Now, the switching patterns of the number of sections of 11
shown in FIGS. 8(a) and 8(b) will be described below. In the
switching patterns, new sections "1'" and "9'" are provided before
the first section and after the ninth section of the patterns shown
in FIGS. 7(a) and 7(b) and respectively connected to reference
potentials to increase the sections of zero vector. A connecting
time in this case can be expressed by a below-described
formula.
[Mathematical Formula 5]
[0164] total time of sections 1 ' + 3 and total time of sections
##EQU00015## 7 + 9 ' = T s 2 ( 1 - ( E max - E min ) ( V max - V
min ) { E max ( E max - E mid ) - E min ( E mid - E min ) } )
##EQU00015.2##
[0165] This formula is the same as the formula (3) and (8) shown in
the Tables 1 and 2. Other switching times than the above-described
time can be expressed by the same formulas as the formulas (1) to
(10) depending on the state of the reference potential.
[0166] Claim 6 discloses the switching pattern in FIG. 8(a) when
the phase in which the absolute value of the input voltage is
maximum is negative (Emin=Ebase). Claim 7 discloses the switching
pattern in FIG. 8(b) when the phase in which the absolute value of
the input voltage is positive (Emax=Ebase).
[0167] Usually, as the control system of the PWM cyclo-converter, a
two-phase modulation system has been ordinarily employed in which
an output one-phase is fixed to a reference potential and a line
voltage is formed by other two phases. As for the line voltage, an
example for forming the line voltage by a proposed system (the
present invention) is shown in FIG. 9(a). A usual example is shown
in FIG. 9(b). Both in FIGS. 9(a) and 9(b), potentials are switched
nine times. This phenomenon indicates that a switching loss is the
same between the two-phase modulation system as the usual system
and the system of the present invention.
[0168] However, when a low voltage is outputted, in the case of the
usual system, the areas of dVmax and dVmid2 are large, the width of
a pulse needs to be reduced. In that case, the voltage is not
accurately outputted depending on a switching condition to cause a
voltage error. However, in the case of the proposed system of the
present invention, a characteristic modulation system and a
efficient switching pattern are employed as described above. Thus,
even when a command is decreased, the switching time of the phase
voltage is not shortened, so that the voltage can be accurately
outputted even under the low voltage.
[0169] When an electric motor is driven by using the PWM
cyclo-converter, the output voltage needs to be lowered when the
electric motor is driven at low speed. However, in the usual
system, a problem arises that the voltage accuracy is deteriorated
during outputting the low voltage. Thus, the present invention is
employed so that the voltage can be accurately outputted. The
present invention is extremely effectively applied as an
indispensable technique to drive the electric motor from a low
speed with good accuracy.
* * * * *